January 2 - Tue

Mehmed IV (1642–1693) was the Sultan of the Ottoman Empire from 1648 to 1687. He came to the throne at the age of six, and went on to become the second longest reigning sultan in Ottoman history. During his middle years, he oversaw the revival of the empire's fortunes associated with the Köprülü era. Mehmed was known by contemporaries as a particularly pious ruler, and was referred to as gazi, or "holy warrior" for his role in the empire's many conquests. In 1687, after being overthrown, Mehmed retired to Edirne, where he resided until his death.Painting: Unknown

January 5 - Fri

A female limosa harlequin frog (Atelopus limosus) in Panama. This endangered species of toad in the family Bufonidae inhabits stream banks in tropical moist lowland forests and rivers of the Chagres watershed. It is found in two colour forms, one in lowlands and one in uplands.Photograph: Brian Gratwicke

January 18 - Thu

The Wikipedia blackout was a 24-hour period in which access to all articles on the English Wikipedia, barring those on the protested Stop Online Piracy Act and PROTECT IP Act, was suppressed. From January 18–19, 2012, visitors to the website saw only a protest message and the phrase "Imagine a world without free knowledge." It is estimated in excess of 160 million people viewed the banner, which was one of numerous protest actions undertaken at the time. The political environment regarding both bills shifted significantly following the protests, and both were removed from further voting.Image: Wikipedia

January 19 - Fri

Waiting is a pastel on paper by the French ImpressionistEdgar Degas, completed between 1880 and 1882. Part of a series of pastels, paintings, mixed media drawings and sculptures of ballerinas, it depicts one accompanied by her chaperone, bent over ostensibly to massage her foot but with body language indicating anticipation. The work, which is jointly owned by the Norton Simon Art Foundation, Pasadena, and the J. Paul Getty Museum, Los Angeles, has been read as emphasizing the brevity of a ballerina's career and the stress they undergo to obtain fleeting moments of elegance.Painting: Edgar Degas

January 20 - Sat

A portrait of a cheetah at Whipsnade Zoo in Bedfordshire. Cheetahs have small and streamlined heads. Their ears are small, short, and rounded, marked by black patches on the back and tawny edges. Their high-set eyes have round pupils, while their whiskers are fine and inconspicuous. Their faces have unique "tear streak" markings that may serve to reduce glare or define facial expressions.Photograph: William Warby

January 23 - Tue

Allegory of Vanity, a vanitas completed by Antonio de Pereda between 1632 and 1636. Works in this category of symbolic art, especially associated with still life paintings of 16th- and 17th-century Flanders and the Netherlands, refer to the traditional Christian view of earthly life and the worthless nature of all earthly goods and pursuits. The Latin noun vanĭtās means "emptiness" and derives its prominence from Ecclesiastes. Common symbols in vanitas include skulls, rotten fruit; bubbles; smoke, watches, hourglasses, and musical instruments.Painting: Antonio de Pereda

January 27 - Sat

Masked lovers during the 2010 Carnival of Venice, an annual festival held in Venice, Italy, which ends on Shrove Tuesday. Although it traces its roots to the 12th century, the current festival only began in 1979, when the Italian government used the Carnival as the centerpiece of its efforts to bring back the history and culture of Venice. Elaborate masks such as those shown here play a central role in the festival, and have become part of popular culture.Photograph: Frank Kovalchek

January 28 - Sun

Rho Ophiuchi is a multiple star system in the constellationOphiuchus. The central system has an apparent magnitude of 4.63. Based on the central system's parallax of 9.03 mas, it is located about 360 light-years (110 parsecs) away. The other stars in the system are slightly farther away.Photograph: Rogelio Bernal Andreo